Stability of Calcium Carboaluminate Prepared by One-Step Method Under Various Environmental Conditions

doi:10.16552/j.cnki.issn1001-1625.2025.1237

Abstract

Abstract:

This study used a one-step method to prepare calcium carboaluminate （MC）， which involved the direct reaction of calcium sources， aluminum sources， and carbonate sources at temperatures of 80， 90， and 100 ℃. The stability of the prepared MC in solutions with different pH levels， temperatures， and concenrations of chloride salt， sulfate， and its mixed salt environments was investigated using X-ray diffraction， scanning electron microscopy， and thermogravimetric analysis. The results indicate that MC prepared via the one-step method exhibits excellent chemical stability in alkaline environments （pH≥11）. The initial decomposition temperature of MC is 130 ℃， and it completely decomposes into CaO and Al（OH）₃ at 450 ℃. In chloride solutions， MC readily immobilizes free Cl^- to form Friedel’s salt. The immobilization efficiency shows a positive correlation with the Cl^- concentration， and MC prepared at 90 ℃ demonstrates the highest Cl^- reactivity. In sulfate solutions， MC easily reacts with $S O 4 2 -$ to form ettringite. In CaCl₂-Na₂SO₄ mixed salt solution， $S O 4 2 -$ has a higher reaction priority than Cl^-. At a low concentration （0.2 mol/L） of the mixed salt solution， the main products are ettringite and calcium carbonate， while at high concentrations （0.5 and 1.0 mol/L）， the products shift predominantly toward calcium sulfate dihydrate phases. This study provides new insights and experimental support for the feasibility of using one-step MC as a corrosion inhibitor for steel reinforcement in practical engineering， confirming that its stability is closely related to the synthesis temperature， as well as the type and concentration of environmental ions.

Key words: one-step method, calcium carboaluminate, acid-alkali stability, chloride ion corrosion inhibition, corrosion inhibitor

CLC Number:

TU375

WANG Yingxiang, DING Tianhui, JI Zhijiang, XIE Shuai, WU Zihao, MA Chao, YU Haiyan. Stability of Calcium Carboaluminate Prepared by One-Step Method Under Various Environmental Conditions[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(6): 1968-1978.

Figures/Tables 10

Fig.1 XRD patterns of MC prepared by one-step method

Table 1 Solution specification and soaking time

CaCl₂ concentration/（mol·L^-1）	Na₂SO₄ concentration/（mol·L^-1）	Solid-to-liquid ratio	Soaking time/d
0.2	—	1∶50	7
0.2	—	1∶50	14
0.2	—	1∶50	28
0.2	—	1∶50	56
0.5	—	1∶50	7
0.5	—	1∶50	14
0.5	—	1∶50	28
0.5	—	1∶50	56
1.0	—	1∶50	7
1.0	—	1∶50	14
1.0	—	1∶50	28
1.0	—	1∶50	56
—	0.2	1∶50	3
—	0.2	1∶50	7
—	0.2	1∶50	14
—	0.2	1∶50	28
—	0.5	1∶50	3
—	0.5	1∶50	7
—	0.5	1∶50	14
—	0.5	1∶50	28
—	1.0	1∶50	3
—	1.0	1∶50	7
—	1.0	1∶50	14
—	1.0	1∶50	28
0.1	0.1	1∶50	3
0.1	0.1	1∶50	28
0.1	0.1	1∶50	56
0.25	0.25	1∶50	3
0.25	0.25	1∶50	28
0.25	0.25	1∶50	56
0.5	0.5	1∶50	3
0.5	0.5	1∶50	28
0.5	0.5	1∶50	56

Table 2 Supernatant pH value of MC soaked in solutions with different initial pH values for varying durations

Initial pH value		3.0	5.0	7.0	8.0	9.0	10.0	11.0	12.0
Supernatant pH value	3 d	11.0	12.0	13.0	12.5	13.0	12.0	12.0	12.0
	7 d	10.5	11.0	11.5	12.0	12.5	12.5	12.0	12.0
	14 d	10.5	11.0	10.5	11.5	12.0	12.5	12.5	12.0

Fig.2 XRD patterns of MC soaked in solutions with different initial pH values for varying durations

Fig.3 XRD patterns and TG-DTG curve of MC after treatment at different temperatures

Fig.4 SEM images of MC after treatment at different temperatures

Fig.5 XRD patterns of MC soaked in CaCl2 solutions with different concentrations for varying durations

Fig.6 XRD patterns of MC soaked in Na2SO4 solutions with different concentrations for varying durations

Fig.7 SEM images of MC prepared at 90 ℃ after soaked in Na2SO4 solutions with different concentrations for 3 d

Fig.8 XRD patterns of MC soaked in CaCl2-Na2SO4 mixed salt solutions with different concentrations for varying durations

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